The present invention relates to a gas pressure gauge which measures the pressure of a gas by using a quartz vibrator.
A quartz-type gas pressure gauge has heretofore been known in which a single sensor is capable of measuring the gas pressure of from atmospheric pressure through up to 10.sup.-3 Torr. That is, since it was found that resonance resistance of a quartz vibrator exhibits dependency upon the pressure of ambient atmosphere over a wide range, gas pressure gauges have been developed in which a single sensor measures the pressure of from atmospheric pressure through up to 10.sup.-3 Torr by utilizing the above-mentioned phenomenon. This has been disclosed in, for example, "Keiso" (Development of a very small Vacuum Sensor using a Quartz Vibrator), Vol. 27, No. 7, 1984.
In the quartz-type gas pressure gauge of the above-mentioned conventional structure which utilizes the resonance resistance of a quartz vibrator that changes depending upon the pressure, however, the resonance resistance of quartz vibrator greatly changes in a low pressure region of 10.sup.-3 to about 10.sup.-2 Torr, making it difficult to take measurement maintaining precision.
FIG. 4 illustrates temperature characteristics of resonance resistance of a conventional quartz vibrator. In vacuum, the resonance resistance greatly changes with the change in the temperature, i.e., the resonance resistance increases with the increase in the temperature. In the open air, on the other hand, the resonance resistance is mostly affected by friction with the air, and does not greatly change even when the temperature is changed. According to the conventional technique, therefore, the resonance resistance is seriously affected by the temperature as the gas pressure decreases, and error develops in the measurement.
It is an object of the invention to provide a quartz-type gas pressure gauge having a resonance varies little depending upon the temperature under low pressure conditions, making it possible to obtain meanurement maintaining increased precision under low-pressure condition.
Other and further objects, features and advantages of the invention will appear more fully from the following description.